Then you use etcd or consul. I would claim that release a new feature by enabling additional code path across multiple apps at once is a bit of an anti-pattern

Then you use etcd or consul. I would claim that release a new feature by enabling additional code path across multiple apps at once is a bit of an anti-pattern. It seems rather dangerous and error prone. In that case I'd actually release it in reverse order, so to speak. Release the apps that use the services of others first and have it check is this service is available/functional and if not, skip calling it. The release the feature to the next service down the stack. Then you can always rollback the last service and be confident that the callers still work. It's way more work and I can see why for certain types of application isn't not really worth the trouble.